In the structural geology of Arunachal Pradesh, the major tectonic fault line that separates the Lesser Himalayas from the Sub-Himalayan Siwalik belt is known as:

💡 Solution & Explanation

The Main Boundary Thrust is the major regional fault separating the tertiary sedimentary rocks of the Siwalik foothills from the older metamorphic and sedimentary formations of the Lesser Himalayas. The Main Central Thrust lies further north, separating the Lesser Himalayas from the Higher Himalayas. The suture zone marks the ancient collision boundary between the Indian and Eurasian plates far to the north. Understanding these structural boundaries is crucial for seismic zonation and resource exploration.